With recent medical developments, the human life expectancy is becoming longer, however, the ratio of cardiac failure to all the various causes of death is also increasing. Ventricular assist devices have become increasingly recognized as potentially able to allow patient's whose natural heart is diseased or has been injured by trauma or heart attack, to recover and continue life, either while their natural heart heals, while awaiting a heart transplant, or even on a long-term basis.
In particular, left-ventricular assist devices (LVAD) are recognized as potentially very valuable for assisting patients who suffer from congestive heart failure. The LVAD was developed for the treatment of end stage congestive heart failure in patients who are on maximal medical therapy and require long-term mechanical circulatory support, for example, patients who are not (temporarily or permanently) candidates for heart transplantation.
A LVAD is able to assume the function of the left ventricle, and thus continue perfusion of oxygen-rich blood into the body. The LVAD attaches to the patient's natural heart, and to a natural artery, and can be removed if the natural heart recovers. Some LVADs are surgically implanted into the patient's abdominal cavity, while others remain outside the body and are placed in fluid communication with the heart via elongated cannulas. Blood flow in the LVAD is effected by expansion and contraction of a variable-volume chamber. One-way valves associated with the inflow and outflow ports of the LVAD provide for blood flow into the variable-volume chamber during expansion, and for blood flow out of this chamber, usually to the ascending thoracic aorta. A pair of conduits respectively connect the inlet port of the assist device to the left ventricle and the outlet port to the major artery which is to receive the blood flow from the device. A typical LVAD is shown and described in U.S. Pat. No. 6,001,056, the entire contents of which are hereby incorporated by reference.
Alternatively, a VAD can be applied to replace or augment the function of the right ventricle (RVAD). As such, for the purposes of the present invention, the use of VAD applies to both LVADs and RVADs.
With reference to FIG. 1, a patient 10 is shown in fragmentary front elevational view. Surgically implanted into the patient's abdominal cavity 12 is the pumping portion 14 of a ventricular assist device, generally referenced with the numeral 16. The ventricular assist device 16 includes an inflow conduit 18 conveying blood from the patient's left ventricle into the pumping portion 14, and an outflow conduit 20 conveying blood from the pumping portion 14 to the patients ascending thoracic aorta. From the pumping portion 14, a power cable 22 extends outwardly of the patient's body via an incision to a compact controller 24. A power source, such as a battery pack worn on a belt about the patient's waist, and generally referenced with the numeral 26, is connected with the controller 24.
Each of the conduits 18, 20 includes a tubular metallic housing proximate the pumping portion 14 of the device which may connect to elongated flexible segments extending to the heart and ascending aorta, respectively. At the end of the inflow conduit 18 which is connected to the patient's heart, and at the end of the outflow conduit 20 which is connected to the ascending thoracic aorta, the conduits are generally attached to the natural tissue by sutures through the use of an apical sewing ring so that blood flow communication is established and maintained.
The distal end of the inflow conduit 18 is inserted through the ventricle wall and into the heart in order to establish blood flow from the heart to the pumping portion 14. The length of the inflow conduit which passes through the ventricle wall and into the heart is important in order to avoid blood clotting while still ensuring adequate blood flow. If for example, the length of inflow conduit which is inserted into the heart is too great, the tip of the inflow conduit will touch the opposing wall or the septum wall of the heart and thereby suction tissue into the conduit. On the other hand, if the length of the inflow conduit is too short, tissue and muscle ingrowth around the conduit tip opening will eventually create an occlusion, thereby blocking the conduit and preventing an adequate blood flow. Obtaining the appropriate length of inflow conduit is difficult to achieve, however, because while the inflow conduit is generally a fixed length, the thickness of the ventricular wall varies depending upon the patient.
Accordingly, there exists a need for a reliable and efficient system for adjusting the length of the inflow conduit which extends interior to the ventricular wall of the heart during implantation of a VAD.